Structures made from portland cement concrete, especially bridge decks, prematurely deteriorate due to wear from exposure to traffic, severe weather conditions and improper application of the concrete or errors in engineering. These structures develop cracks that compromise the integrity of the concrete and expose the reinforcing bars to corrosive elements. Additionally, after a few freeze/thaw cycles, cracks develop into holes that require repair. Many strategies have been employed in an attempt to protect and repair these structures, including providing a protective latex modified concrete overlay, epoxy coating the reinforcing steel, providing an asphaltic concrete/membrane system and feeding a low viscosity, low modulus polymer into the cracks in concrete decks.
One system used to protect portland cement concrete structures is an application of acrylate or methacrylate monomers that cures to form a hard and durable coating on/in concrete.
U.S. Pat. No. 4,341,673 to Hyde relates to methacrylate polymer concrete compositions wherein the tendency of polymer concrete to shrink during cure is reduced by incorporating 5-12% by weight of a paraffinic oil containing at least 60% of saturated aliphatic hydrocarbons and 4-10% by weight of a liquid mixture of an acrylic polymer. This patent teaches that both of these components are needed to achieve the desired properties of the polymer concrete.
U.S. Pat. No. 3,203,921 to Rosenfelder discloses resin compositions of monoolefin polymers, a predominantly aliphatic, paraffinic hydrocarbon mineral oil and mineral filler. The monoolefin may be copolymerized with acrylate polymers. The paraffinic mineral oil reduces the brittleness of these compositions, in addition to gloss and waxy appearance of the ultimate articles prepared therefrom.
U.S. Pat. No. 4,910,080 to Frost discloses impregnating compositions for porous substrates comprising dicyclopentenyl acrylate or methacrylate together with a C.sub.5 to C.sub.8 alkyl ester of acrylic or methacrylic acid.
U.S. Pat. No. 4,263,372 to Emmons et al. discloses coating compositions for porous substances comprising dicyclopentenyl acrylate or methacrylate, together with a non-volatile acrylate or methacrylate. At col. 4, lines 3-16, enhancement of the cure rate by providing a subsequent application of an immiscible liquid surface coating to block exposure to air is disclosed.
Coating compositions that have been previously used suffer from the disadvantage of requiring a long period of time to cure. This is especially troublesome when the structure to be treated is an integral component to a community transportation system, such as a bridge. When the coating system takes longer than about six hours to cure, traffic may have to be diverted during the "rush hours." Acrylate and methacrylate compositions particularly exhibit long cure times when the ambient temperature goes below about 20.degree. C., or in dark environments such as lower decks in multiple level structures or at night or on cloudy days. There is a need for acrylate or methacrylate coating compositions that will cure to a non-tacky state in a relatively short time, for example less than about 8 hours, even under less than ideal conditions.